Fans of the Unreal Tournament series will be happy to hear that two new game modes will be included in Unreal Tournament 2004. The new modes include Onslaught, along with the return of the classic assault mode. Here's more detailed descriptions of the modes courtesy of Epic's Mark Rein:

Assault Mode - The much heralded single-player oriented gametype returns with all-out battles with land, space and air-based vehicles on the home worlds of various Unreal Tournament 2004 combatants. In one scenario, players will experience the adrenaline rush of space-based battle while attacking or defending a Skaarj mother ship. Another scenario takes place on Xan Kriegor's mechanical home world where players attack or defend a robot construction factory. There are currently six Assault scenarios planned to ship with the game. Onslaught Mode - New multi-player oriented combat game type on custom-built large-scale maps featuring awesome new weapons and land- and air-based vehicles. From the lethal bomber to the nefarious spider mines - players will work as teams to control map points and win the conflict. There are currently nine Onslaught maps planned to ship with the game.